Winslow Townson/The Associated PressBoston Celtics forward Glen Davis, left, goes up against Los Angeles Lakers center Andrew Bynum during the second quarter in Game 4 of the NBA Finals on Thursday night in Boston.

Bynum tweaked his knee in Game 3 after attempting to block a shot by Boston center Kendrick Perkins.

In preparation for Thursday, Bynum went through an extended therapy session Wednesday.

Early in the game, Bynum hit the floor hard after trying to stop Paul Pierce from penetrating into the lane after he had gotten past Ron Artest. Bynum resumed playing, but after the first timeout, he was replaced by forward Lamar Odom. Bynum was limited to playing seven minutes in the first half.

“We will try to get him six, seven minutes at the beginning of the game, ’’ Lakers Coach Phil Jackson said before the game. ”He likes to get out there and participate.’’

Bynum has torn cartilage in his right knee and put off surgery so he could participate in the Finals.

Two years ago, Bynum required knee surgery and missed playing in the Finals in which the Lakers lost to the Celtics in six games.

“I’m doing OK, ’’ Bynum said. ”But if come down, and I try to jump up again, I feel that, running and stopping, running really hard and stopping. It’s just something I have to deal with. It’ll hurt and then go away.’’

If Bynum had been unavailable, Jackson was prepared to shift power forward Pau Gasol to center and move Odom into the starting lineup.

Bynum’s contribution had been significant in the first three games, averaging 13.3 points and 7.3 rebounds.

“I think the big factor is that he knows he’s going to be in some kind of discomfort during the course of the game, ’’ Jackson said. ”It comes and goes. He feels a sharp pain when he makes certain movements, but he understands how that comes and goes, so it’s not something he gets concerned about.’’

TOUGH TO MAKE IMPACT: Ray Allen made the Celtics’ first field goal of Game 4, then missed his next five attempts.

He was aiming to bounce back after missing all 13 shot attempts in Tuesday’s Game 3. Celtics forward Kevin Garnett also struggled to make an impact early after missing three of his first four shots. But he made a last-second shot just before the buzzer to cut the Lakers’ lead to 45-42. Garnett led the Celtics with 25 points on 11-of-16 shooting in Game 3. Paul Pierce found his shooting rhythm quickly in Game 4, hitting four of his first six shots to score 10 of the Celtics’ first 14 points.

OFFICIATING COMPLAINT: Boston Celtics Coach Doc Rivers has had harsh criticism for the officiating in the Finals. Rivers sent a tape to the NBA office on Wednesday that supposedly showed numerous illegal screens set by the Lakers in Game 3 that were not called by the officiating crew of Bennett Salvatore, Bill Kennedy and Dan Crawford.

“I don’t usually send in a lot to the league, but I sent in a lot (Wednesday morning), ’’ Rivers said.

Entering Game 4, the Lakers had been called for 75 fouls compared with the Celtics’ 84. But after the first quarter Thursday night, both teams combined had only eight fouls.